import math


def distance(p1, p2):
    """returns the distance between p1 and p2

    >>> d = distance((0, 0), (1, 1))
    >>> print("{0:.5f}".format(d))
    1.41421
    """
    (x1, y1) = p1
    (x2, y2) = p2
    return math.sqrt((x2-x1)**2 + (y2-y1)**2)


def run():
    x1, y1, x2, y2 = [float(i) for i in input().split()]

    print(distance((x1, y1), (x2, y2)))


if __name__ == '__main__':
    run()
 import math math def distance(p1, p2):
    """returns the distance between p1 and p2

    >>> d = distance((0, 0), (1, 1))
    >>> print("{0:.5f}".format(d))
    1.41421
    """
    (x1, y1) = p1
    (x2, y2) = p2
    return math.sqrt((x2-x1)**2 + (y2-y1)**2) distance """returns the distance between p1 and p2

    >>> d = distance((0, 0), (1, 1))
    >>> print("{0:.5f}".format(d))
    1.41421
    """ (x1, y1) = p1 (x1, y1) x1 y1 p1 (x2, y2) = p2 (x2, y2) x2 y2 p2 return math.sqrt((x2-x1)**2 + (y2-y1)**2) math.sqrt((x2-x1)**2 + (y2-y1)**2) math.sqrt math sqrt (x2-x1)**2 + (y2-y1)**2 (x2-x1)**2 x2-x1 x2 x1 2 (y2-y1)**2 y2-y1 y2 y1 2 p1 p1 p2 p2 def run():
    x1, y1, x2, y2 = [float(i) for i in input().split()]

    print(distance((x1, y1), (x2, y2))) run float(i) for i in input().split() for i in input().split() i input().split() ().split () input split for i in input().split() float(i) float i x1, y1, x2, y2 = [float(i) for i in input().split()] x1 [float(i) for i in input().split()] y1 x2 y2 print(distance((x1, y1), (x2, y2))) print distance((x1, y1), (x2, y2)) distance (x1, y1) x1 y1 (x2, y2) x2 y2 if __name__ == '__main__':
    run() __name__ == '__main__' __name__ '__main__' run() run def distance(p1, p2):
    """returns the distance between p1 and p2

    >>> d = distance((0, 0), (1, 1))
    >>> print("{0:.5f}".format(d))
    1.41421
    """
    (x1, y1) = p1
    (x2, y2) = p2
    return math.sqrt((x2-x1)**2 + (y2-y1)**2) def distance(p1, p2):
    """returns the distance between p1 and p2

    >>> d = distance((0, 0), (1, 1))
    >>> print("{0:.5f}".format(d))
    1.41421
    """
    (x1, y1) = p1
    (x2, y2) = p2
    return math.sqrt((x2-x1)**2 + (y2-y1)**2) distance def run():
    x1, y1, x2, y2 = [float(i) for i in input().split()]

    print(distance((x1, y1), (x2, y2))) def run():
    x1, y1, x2, y2 = [float(i) for i in input().split()]

    print(distance((x1, y1), (x2, y2))) run
import math


def distance(p1, p2):
    """returns the distance between p1 and p2

    >>> d = distance((0, 0), (1, 1))
    >>> print("{0:.5f}".format(d))
    1.41421
    """
    (x1, y1) = p1
    (x2, y2) = p2
    return math.sqrt((x2-x1)**2 + (y2-y1)**2)


def run():
    x1, y1, x2, y2 = [float(i) for i in input().split()]

    print(distance((x1, y1), (x2, y2)))


if __name__ == '__main__':
    run()

